Phase shifting of a Signal - RF Cafe Forums
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Post subject: Phase shifting of a Signal Posted: Tue Nov 01, 2005 3:31 am
How do you shift the Phase of an analog signal.
With digital its so easy, you just put a delay of couple of usecs and you get a phase shifted signal.
How do you do it in analog?
Post subject: Analog phase shiftPosted: Tue Nov 01, 2005 2:22 pm
There are several ways of shifting the phase of an analog signal:
1. Use the appropriate length of cable: 90 degrees is one-quarter wavelength (don't forget to include the velocity factor of the cable!)
2. Artificial delay lines are also a possibility at frequencies low enough that a piece of cable would be unreasonably long. These simulate a piece of cable by series / parallel C circuits, cascaded. Other kinds of LC networks are also possible if you don't want constant time delay.
3. RC Networks: the phase shift is 45 degrees at f = 1/(2 pi RC) for a simple two-component high-pass or low-pass. More complicated networks can be used to shape phase as a function of frequency.
Obviously, some techniques (RC) are lossy, some (transmission lines) have very little loss.
Post subject: Posted: Wed Nov 02, 2005 1:37 pm
Are you aware of any manufactureres that make Delay lines for analog signals. It should be variable delay, not one of those fixed -10%, 20% delays.
Post subject: Phase ShiftPosted: Thu Nov 03, 2005 1:30 am
I haven't checked their recent catalogs, but Data Delay Devices Inc. used to make such things.
Post subject: Posted: Thu Nov 10, 2005 2:12 pm
i found a new way - using an all pass filter to delay the phase. I can change the phase by varying the resistace. Only problem is the output amplitude is not constant at my frequency - 6Mhz.
It works fine in the Khz range.
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